Many spacecraft carry cryogenic liquids for use as propellants in accomplishing various trajectory adjustments while in orbit. Heat is continually absorbed by the cryogenic liquid which results in an increase in the pressure and temperature in the tank in which the liquid is maintained. Because of weight concerns, the tank is typically a relatively low pressure vessel. Thus, tank pressure and temperature must be controlled to avoid undesirable build-up and this is conventionally controlled by venting vapor from the tank.
However, because of the zero gravity condition experienced by the spacecraft, the liquid and vapor phases within the tank are not separated to allow vapor to be vented to the exclusion of the liquid. Thus, separation of the phases to allow venting of only vapor has conventionally been accomplished by accelerating the vehicle in its orbit causing the liquid, because of its greater density, to separate from the vapor. In many instances, this is a satisfactory means of handling the problem. However, in some instances, as in the case of a liquid fueled rocket carried in the cargo bay of a space shuttle, such a method of separating liquid from the vapor cannot be used while the rocket remains within the cargo bay while the shuttle is in orbit.
Thus, the present invention is directed to overcoming the problem of venting vapor build-up and to providing a unique heat exchanger that may be used in overcoming such problem.